Three-phase transformerless inverter for PV grid connected system with zero common mode noise

Abstract

The problem of common mode noise in transformerless grid-connected PV inverters has triggered the concerns of many researchers due to the negative impacts that can cause to the system. Most of the topologies were based on modifying the structure of the inverter or on proposing new modulation techniques. In single-phase system, the concept of the common ground between the PV negative terminal and the neutral point of the grid was the only topology that eliminate completely the leakage current. However, none of the existing threephase inverters was able to totally eliminate this CM noise. Therefore, this thesis proposes a three-phase inverter based on the successful concept applied in the single-phase system. The goal of this project is to have a three-phase inverter that can totally eliminate the leakage current. In order to achieve this task, three single-phase inverters were connected in parallel in order to form the three-phase topology. The proposed inverted was implemented with a PV array, appropriate modulation technique, corresponding inverter controller including a maximum power point tracker and a current controller, and a three-phase Y-connected AC grid voltages. The implementation and simulation of the overall system were done using Matlab/Simulink software. The results of the simulation proved the excellent performance of the proposed topology and confirmed its goal in achieving a zero common mode noise by totally eliminating the leakage current.